drm/xe/guc: Convert GuC registers to REG_FIELD/REG_BIT

Cleanup GuC register declarations by converting them to use REG_FIELD,
REG_BIT and REG_GENMASK. While converting, also reorder the bitfields
so they follow the convention of declaring the higher bits first.

v2:
  - Drop unused HUC_LOADING_AGENT_VCR and DMA_ADDRESS_SPACE_GTT (Matt Roper)
  - Simplify HUC_LOADING_AGENT_GUC define (Matt Roper)

Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
Link: https://lore.kernel.org/r/20230427223256.1432787-2-lucas.demarchi@intel.com


Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>